Refrigerant compositions having a siloxane solubilizing agent

ABSTRACT

Provided are refrigerant compositions which are blends of one or more hydrofluorocarbons, siloxanes, hydrocarbons and lubricants, as well as methods for using these compositions in applications such as the recharging of refrigeration systems and for replacing a chlorofluorocarbon or hydrochlorofluorocarbon in a refrigeration system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of U.S. Provisional PatentApplication No. 61/048253, filed Apr. 28, 2008, which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to a solubilizing agent for a refrigerant. Moreparticularly, this invention relates to a solubilizing agent forimproving the miscibility of conventional lubricants fluorinated-alkane,-alkene, and -ether refrigerants.

2. Description of The Related Art

Certain chlorofluorocarbons (CFCs) and hydrochlorofluorocarbon (HCFCs),such as dichlorofluoromethane (R-12), monochlorodifluoromethane (R-22),and azeotropic mixtures of monochlorodifluoromethane andchloropentafluoroethane (R-115) (known as R-502), have thermodynamicproperties and chemical stability that make them useful as refrigerants.However, these chlorine-containing refrigerants are believed tointerfere with the Earth's ozone layer. Therefore, the use of CFCs andHCFCs have become highly regulated and disfavored for heating andcooling applications.

Certain hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs),hydrofluoroethers (HFEs), and blends thereof are of particular interestas alternatives to CFCs and HCFCs because they have properties that aresimilar to chlorofluorocarbons, including similar refrigerationcharacteristics, but are much more environmentally friendly. Many ofthese compounds have vapor pressure that is ±20 percent of a comparableCFC or HCFC refrigerant at the same temperature, and have similarchemical stability, low toxicity, non-flammability, efficiency in-use,and low temperature glides.

HFCs known to be exceptionally good refrigerants include difluoromethane(R-32), 1,1,1,2,2-pentafluoroethane (R-125), 1,1,1-trifluoroethane(R-143a), 1,1,1,2-tetrafluoroethane (R-134a), and 1,1-difluoroethane(R-152a). Certain blends of two or more of these HFCs can also be usedto achieve particular thermodynamic properties. Common HFC blendsinclude an azeotrope-like blend of R-143a and R-125 (known as R-507A), anon-azeotropic blend of R-125, R-143a, and R-134a (known as R-404A), anon-azeotropic blend of R-32 and R-125 (known as R-410A), and anon-azeotropic blend of R-32, R-125, and R-134a (known as R-407C). Thesealternative refrigerants are available commercially from various sourcesincluding Honeywell International Inc. of Morristown, N.J.

Each of these HFCs or HFC blends can serve as a replacement for one ormore CFCs or HCFCs. For example, R-134a can serve as replacement of R-12in refrigeration and air conditioning applications such as chillers;R-404A and R-507A can serve as replacements for R-502 in mostrefrigeration applications, including high, medium and low evaporationtemperature systems; R410A can serve as replacement of R-22 in new airconditioning and refrigeration equipment: and R-407C can serve as areplacement for R-22 in various air-conditioning applications, as wellas in most refrigeration systems including chillers. It has also becomedesirable to retrofit chlorine-containing refrigeration systems byreplacing chlorine-containing refrigerants with non-chlorine-containingrefrigerants that will not deplete the ozone layer.

To be a feasible refrigerant replacement, the HFC, HFO, or HFE must becompatible with conventional lubricants used in refrigeration systems.Refrigeration system designers are interested in how the lubricantbehaves in the system so that they can design piping and othercomponents to best manage lubricant return to the compressor. Thebehavior of a refrigerant with a lubricant entering the system canaffect film characteristics on heat transfer surfaces, and thus energyefficiency performance. In the absence of solubility, oils tend tobecome lodged in the coils of the compression refrigeration,air-conditioning or heat pump system evaporator, as well as other partsof the system, thereby reducing the system efficiency. Thus, miscibilityof the lubricant with the liquid refrigerant over a wide range ofoperating temperatures is an important consideration in selecting arefrigerant. Unfortunately, many HFCs are relatively insoluble and/orimmiscible in the conventional lubricants, including mineral oils thatare miscible with HCFCs. For example, mineral oil and alkyl benzenes,which have been used with conventional refrigerants such as R-12, R-502and R-22, are immiscible with HFCs. This lack of lubricant compatibilityhas hindered the commercial use of many HFC as refrigerants.

HFC have been used as refrigerants in combination with alternativelubricants such as polyol ester (POE) or other synthetic lubricants.However, retrofitting refrigeration systems with HFC refrigerants isstill problematic. More particularly, retrofitting refrigeration or airconditioning systems with HFC refrigerants typically requires drainingas much of the lubricant oil as possible before introducing the newrefrigerants with synthetic lubricants. This process often involvesremoving the compressor from the system so that the lubricant can beadequately drained. For these and other reasons, it would be highlydesirable to retrofit a CFC or HCFC system with HFCs without having toremove the system's lubricant. If HFCs could be used with conventionallubricants, such a retrofit would become a simple “drop-in” operation.That is, the existent refrigerant would be replaced with a newrefrigerant without any further change in, or disassembly of the systemhardware.

Accordingly, there exists a need to improve the solubility of HFCs inconventional refrigeration lubricants.

SUMMARY OF THE INVENTION

Applicants have discovered that the miscibility of an HFC inconventional lubricants is unexpectedly and significantly increased byblending the HFC with a solubilizing agent comprising one or moresiloxanes, and optionally, one or more hydrocarbons (HCs). In addition,it has been found that certain blends of HFCs, siloxanes, and HCsgenerally retain the thermodynamic properties of the HFC alone.Accordingly, blends of HFCs, HCs and siloxanes can be used to retrofitHCFC refrigeration systems without having to drain or replace thesystem's conventional lubricants.

In one aspect, the present invention provides a composition comprising:(a) a refrigerant selected from the group consisting of ahydrofluorocarbon, hydrofluoroolefin, hydrofluoroether, and blendsthereof; (b) a solubilizing agent comprising at least one siloxane and,optionally, at least one hydrocarbon selected from the group consistingof: C₁-C₆ branched or straight chain alkane, alkene, or alkyl, and aC₃-C₆ cyclic hydrocarbon; and (c) a refrigeration system lubricant.

In another aspect of the invention, provided is a method for recharginga refrigerant system comprising: (a) removing at least a portion of achlorine-containing refrigerant from a refrigeration system comprisingsaid chlorine-containing refrigerant and a lubricant, while retaining amajority of said lubricant in said system; and (b) adding a replacementrefrigerant composition to said refrigeration system either subsequentto, or simultaneously with, said removing step, wherein said replacementrefrigerant composition comprises a refrigerant selected from the groupconsisting of hydrofluorocarbon, hydrofluoroolefin, hydrofluoroether,and blends thereof; and a solubilizing agent comprising at least onesiloxane and, optionally, at least one hydrocarbon selected from thegroup consisting of: C₁-C₆ branched or straight chain alkane, alkene, oralkyl, and a C₃-C₆ cyclic hydrocarbon.

In another aspect of the invention, provided is a method for improvingthe solubility of a refrigerant in a lubricant comprising: contacting arefrigerant selected from the group consisting of a hydrofluorocarbon,hydrofluoroolefin, hydrofluoroether, and blends thereof, with alubricant selected from the group consisting of mineral oil, hydrocarbonoil, alkyl benzene oil, white or paraffinic oil, polyalkylene glycols,polyalkylene glycol esters, polyol esters, polyalphaolefins, andcombinations thereof, wherein said contacting is performed in thepresence of a solubilizing agent comprising a siloxane, and optionally,at least one hydrocarbon selected from the group consisting of: C₁-C₆branched or straight chain alkane, alkene, or alkyl, and a C₃-C₆ cyclichydrocarbon.

In yet another aspect of the invention, provided is a refrigerantcomposition comprising a refrigerant selected from the group consistingof a C₁-C₆ hydrofluorocarbon, C₂-C₄ hydrofluoroolefin, C₅-C₆hydrofluoroether, and blends thereof and solubilizing agent comprisingat least one siloxane selected from the group consisting ofhexamethyldisiloxane, octamethyltrisiloxane, hexaethyldisiloxane, andoctaethyltrisiloxane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a commercial refrigeration system comprising a refrigerantcomposition of the present invention; and

FIG. 2 is another commercial refrigeration system comprising arefrigerant composition of the present invention.

DESCRIPTION OF THE INVENTION

The compositions of the present invention are particularly useful asrefrigerants in compression-type refrigeration systems. In certainembodiments, the composition comprises a refrigerant selected from thegroup consisting of a hydrofluorocarbon, hydrofluoroolefin,hydrofluoroether, and blends thereof; a solubilizing agent comprising atleast one siloxane, and optionally, a low-boiling hydrocarbon; and arefrigeration system lubricant.

In certain preferred embodiments, the refrigerant is ahydrofluorocarbon, more preferably a C₁-C₆ hydrofluorocarbon, and evenmore preferably a C₁-C₆ hydrofluorocarbon having a normal boiling pointof from about −90° C. to 80° C. Representative hydrofluorocarbonsinclude: CHF₃ (HFC-23), CH₂F₂ (HFC-32), CH₃F (HFC-41), CF₃CF₃ (FC-116),CHF₂CF₃ (HFC-125), CHF₂CHF₂ (HFC-134), CH₂FCF₃ (HFC-134a), CHF₂CH₂F(HFC-143), CF₃CH₃ (HFC-143a), CHF₂CH₃ (HFC-152a), CHF₂CF₂CF₃(HFC-227ca), CF₃CFHCF₃ (HFC-227ea), (HFC-236ca), CH₂FCF₂CF₃ (HFC-236cb),CHF₂CHFCF₃ (HFC-236ea), CF₃CH₂CF₃ (HFC-236fa), CH₂FCF₂CHF₂ (HFC-245ca),CH₃CF₂CF₃ (HFC-245cb), CHF₂CHFCHF₂ (HFC-245ea), CH₂FCHFCF₃ (HFC-245eb),CHF₂CH₂CF₃ (HFC-245fa), CH₂FCF₂CH₂F (HFC-254ca), CH₂CF₂CHF₂ (HFC-254cb),CH₂FCHFCHF₂ (HFC-254ea), CH₃CHFCF₃ (HFC-254eb), CHF₂CH₂CHF₂ (HFC-254fa),CH₂FCH₂CF₃ (HFC-254fb), CH₃CF₂CH₃ (HFC-272ca), CH₃CHFCH₂F (HFC-272ea),CH₂FCH₂CH₂F (HFC-272fa), CH₃CH₂CF₂H (HFC-272fb), CH₃CHFCH₃ (HFC-281ea),CH₃CH₂CH₂F (HFC-281fa), CHF₂CF₂CF₂CF₂H (HFC-338pcc), CF₃CHFCHFCF₂CF₃(HFC-43-10mee), C₄F₉OCH₃, and C₄F₉OC₂H₅, and combinations thereof. Ofthese, difluoromethane; 1,1,1,2,2-pentafluoroethane;1,1,1-trifluoroethane; 1,1,1,2-tetrafluoroethane; and 1,1-difluoroethaneare particularly preferred.

Combinations of two or more hydrofluorocarbons are also useful asrefrigerants in the present invention. Particularly preferredcombinations include a combination of pentafluoroethane,tetrafluoroethane, and trifluoroethane; a combination ofpentafluoroethane and trifluoroethane; a combination of difluoromethaneand pentafluoroethane; a combination of difluoromethane,pentafluoroethane, and tetrafluoroethane; and a combination ofdifluoromethane, pentafluoroethane, and tetrafluoroethane. Particularlypreferred combinations include HFC-404a, a combination ofpentafluoroethane, tetrafluoroethane, and trifluoroethane in a ratio ofabout 44%:4%:52%; HFC-507a, a combination of pentafluoroethane andtrifluoroethane in a ratio of about 50%:50%; HFC-410a, a combination ofdifluoromethane and pentafluoroethane in a ratio of about 50%:50%;HFC-407a, a combination of difluoromethane, pentafluoroethane, andtetrafluoroethane in a ratio of about 30%:40%:40%; and HFC-407c, acombination of difluoromethane, pentafluoroethane, and tetrafluoroethanein a ratio of about 20%:25%:52%.

These hydrofluorocarbon refrigerants are commercially available, forexample, from Honeywell International Inc of Morristown, N.J.

In certain preferred embodiments, the refrigerant is a hydrofluoroolefin(HFO), preferably having a normal boiling point of about −90° C. to 80°C. More preferably, the hydrofluoroolefin is C₂-C₆ HFO, even morepreferably a C₃-C₄ HFO, and even more preferably a trifluoropropene,tetrafluoropropene, or pentafluoropropane, including each structural andstereoisomer thereof. Examples of preferred HFOs include, but are notlimited to, CF₃CF═CH₂ (HFO-1234yf), 1,3,3,3-tetrafluoropropene(HFC-1234ze), and (Z)-1,1,1,2,3-pentafluoropropene (HFO-1225yeZ).

In preferred embodiments, the solubility agent increases the miscibilityof the refrigerant in a conventional refrigeration system lubricant,such as mineral oil. The solubility agent comprises an effective amountof a high-boiling siloxane, and optionally, may also include alow-boiling hydrocarbon. By high-boiling it is meant a compound having anormal boiling point of about 90° C. or above, more preferably about 90°C. to about 200° C., and even more preferably about 100° C. to about155° C. By low-boiling it is meant a compound having a normal boilingpoint of not more than about 85° C., preferably about −165° C. to about85° C., more preferably about −50° C. to about 10° C., and even morepreferably about −25° C. to about 0° C.

Preferred siloxanes include those of Formula (I):

wherein

-   -   R₁-R₈ is independently H, C₁-C₄ alkyl, or C₆-C₁₀ aryl, and    -   n is an integer from 0 to 10.

In particularly preferred embodiments, n is 1 to 4 and R₁-R₈ isindependently H or C₁-C₃ alkyl, provided that a majority R₁-R₈ is aC₁-C₃ alkyl. In other preferred embodiments, n is 0 or 1 and all ofR₁-R₈ is methyl or all of R₁-R₈ is ethyl (e.g., hexamethyldisiloxane,octamethyltrisiloxane, hexaethyldisiloxane, octaethyltrisiloxane). Aparticularly preferred siloxane is hexamethyldisiloxane.

Solubilizing agents preferably have both a high-boiling siloxane and alow-boiling hydrocarbon. Preferred hydrocarbons include C₁-C₆ branchedor straight chain alkanes, C₂-C₆ branched or straight chain alkenes,C₂-C₆ branched or straight chain alkyls, and C₃-C₆ cycloalkanes. UsefulC₁-C₆ hydrocarbons non-exclusively include methane, ethane, propane,propene, propyne, cyclopropane, 2,2-dimethylpropane, butane, isobutane,2-methylbutane, pentane, isopentane, 3-methylpentane, hexane,cyclohexane, isohexane, or combinations thereof.

As noted above, the solubilizing agent preferably improves themiscibility of hydrofluorocarbon (HFC), hydrofluoroolefin (HFO), andhydrofluoroether (HFE) refrigerants in conventional refrigeration systemlubricants. Such lubricants include mineral oil, hydrocarbon oil, alkylbenzene oil, white or paraffinic oil, polyalkylene glycols, polyalkyleneglycol esters, polyol esters, polyalphaolefins, and combinationsthereof. Useful mineral oils include paraffins (i.e. straight-chain andbranched-carbon-chain, saturated hydrocarbons), naphthenes (i.e. cyclicparaffins) and aromatics (i.e. unsaturated, cyclic hydrocarbonscontaining one or more rings characterized by alternating double bonds).The mineral oils useful for the present invention include those commonlyknown as “synthetic oils” in the field of compression refrigerationlubrication. Synthetic oils comprise alkylaryls (i.e. linear andbranched alkyl alkylbenzenes), synthetic paraffins and napthenes, andpoly(alphaolefins). Commercially available mineral oils include Witco LP250® from Witco, Zerol 300® from Shrieve Chemical, Sunisco 3GS fromWitco, and Calumet R015 from Calumet. Other useful mineral oils arecommercially available as BVM 100 N (paraffinic mineral oil sold by BVAOils), Suniso® 3GS (napthenic mineral oil sold by Crompton Co.), Sontex®372LT (napthenic mineral oil sold by Pennzoil), Calumet® RO-30(napthenic mineral oil sold by Calument Lubricants), Zerol® 75 andZerol® 150 (linear alkylbenzenes sold by Shrieve Chemicals) and HAB 22(branched alkylbenzene sold by Nippon Oil). The chemical compositionsand uses of these oils are well known (see e.g. “FluorocarbonRefrigerants Handbook” by Ralph C. Downing, Prentice Hall, 1998, pp.206-270). Polyalkylene glycol refrigeration lubricants are disclosed inU.S. Pat. Nos. 4,755,316; 4,971,712, and 4,975,212, each of which isincorporated herein by reference. Polyalkylene glycol esters aredisclosed in U.S. Pat. No. 5,008,028 which is incorporated herein byreference.

In a preferred embodiment the HFC, HFO, or HFE is present in therefrigerant composition in an amount of from about 40 weight percent toabout 98.8 weight percent of the overall refrigerant composition, morepreferably about 72 weight percent to about 98.8, and even morepreferably about 85 weight percent to about 99.8 weight percent. In apreferred embodiment the siloxane is present in the refrigerantcomposition in an amount of from about 0.1 weight percent to about 50weight percent of the overall refrigerant composition, more preferablyabout 0.1 weight percent to about 20 weight percent and even morepreferably about 0.1 weight percent to about 10 weight percent. In apreferred embodiment, the hydrocarbon is present in the refrigerantcomposition in an amount of from about 0.1 weight percent to about 10weight percent of the overall refrigerant composition, more preferablyfrom about 0.1 weight percent to about 8 weight percent, and even morepreferably about 0.1 weight percent to about 5 weight percent. In apreferred embodiment, the lubricant is present in the refrigerantcomposition in an amount of from about 1 to about 50 percent by weightof the overall refrigerant composition, more preferably about 1 to about40 percent by weight, and even more preferably about 1 to about 30percent by weight.

The compositions of the present invention may further include any of avariety of optional additives including other lubricants, stabilizers,metal passivators, corrosion inhibitors, flammability suppressants, andthe like. According to certain embodiments, the compositions of thepresent invention further comprise a stabilizer. Any of a variety ofcompounds suitable for stabilizing a composition of the presentinvention may be used. Examples of certain preferred stabilizers includestabilizer compositions comprising stabilizing diene-based compounds,and/or phenol compounds, and/or epoxides. Epoxides include aromaticepoxides, alkyl epoxides, alkenyl epoxides, and combinations thereof.Certain compositions may comprise a diene-based compound in an amounteffective under conditions of use to stabilize the composition againstdegradation. As the term is used herein, “diene-based compound” refersto C₃-C₅ dienes and to compounds formed by reaction of any two or moreC₃-C₅ dienes. In the case of diene-based compounds which are formed by acombination of C₃-C₅ dienes, the molecules which are combined can be thesame or different. In preferred embodiments the diene-based compoundsare selected from the group consisting of allyl ethers, propadiene,butadiene, isoprene, terpenes such as myrcene, terpene derivatives andcombinations of any two or more of these. Any of a variety of phenolcompounds are also suitable for use as stabilizers in the presentcompositions. As used herein the term “phenol compound” refers generallyto any substituted or unsubstituted phenol. Examples of suitable phenolcompounds include phenols comprising one or more substituted orunsubstituted cyclic, straight-chain, or branched aliphatic substituentgroup, such as, alkylated monophenols including:2,6-di-tert-butyl-4-meth-ylphenol; 2,6-di-tert-butyl-4-ethylphenol;2,4-dimethyl-6-tert-butylphenol; tocopherol; and the like. In certainembodiments, the epoxide, diene or phenolic stabilizer compounds may bepresent in the refrigerant composition in amounts of from about 0.001%to about 10% by weight, more preferably from about 0.01 wt. % to about 5wt. %, and even more preferably from about 0.3 wt. % to about 4 wt. %,based on the total weight of the refrigerant composition.

The invention further provides a method of recharging a refrigerationsystem or a refrigeration apparatus may be retrofit with a newrefrigerant composition. The refrigeration system or apparatus to berecharged or retrofit preferably contains a refrigerant comprising achlorofluorocarbon, a hydrochlorofluorocarbons, or combination thereof,along with a lubricant. The old refrigerant composition is removed andsubstituted with the inventive refrigeration composition describedherein.

The refrigerant compositions of the present invention preferably operatein compression-type refrigeration/heat pump system, i.e., therefrigerant circulates in the refrigeration apparatus such that therefrigeration system generates refrigeration. This technique is usefulfor automotive, household and industrial size air conditioners,refrigeration systems and heat pumps. A refrigeration system comprisinga refrigeration apparatus and a refrigerant composition 10 as describedherein circulating in the refrigeration apparatus is show in FIGS. 1 and2.

EXAMPLES

The following non-limiting examples serve to illustrate the invention.

Example 1 Performance

This example demonstrates the thermodynamic properties of a HFC/HMDS andHFC/HMDS/HC blends.

Testing was performed in a refrigeration apparatus under typicaloperating conditions using a refrigerant test mixture and mineral oil(Nu-Calgon C-3 Refrigeration Oil). The test mixtures composition were asfollows:

Blend 1: 96 wt. % of HFC (R407C) and 4 wt. % of HMDS

Blend 2: 97 wt. % of HFC (R407C), 2 wt. % of HMDS and 1 wt % ofisobutane.

Testing was performed using a setup similar to the unit described inReport DOE/CE/23810-71 “Study of Lubricant Circulation in HVAC Systems,”March 1995-April 1996 by Frank R. Biancardi et. al. (prepared for AirConditioning and Refrigeration Technology Institute Under ARTI/MCLRProject No. 665-53100), which is incorporated herein by reference. Inthis case, commercial refrigeration system equipment was employed usinga commercially available condensing unit and an evaporator for a walk-infreezer/cooler (see FIG. 1). The following is a detailed description ofthe equipment:

The condensing unit was as manufactured by Keeprite Refrigeration,Brantford, Ontario Model K350L2 outdoor, air cooled, low temperature,R-22 condensing unit equipped with a 2DF-0300 Copeland compressor, afin-and-tube coil, and a demand cooling system for low temperatureoperation. It also has a suction accumulator, an oil separator, areceiver, a two-valve head pressure control system, and other standardoperating controls.

The evaporator was as manufactured by Keeprite Refrigeration. A ModelKUCB204DED electric defrost, low profile DX fed evaporator with electricdefrost heaters and a Sporlan distributor and TXV. Capacity was rated as17,340 BTUH @−20° F. SST, 10 degree TD, and 3,200 CFM air flow. Theevaporator was installed in an environmentally controlled chamber thatserved as the walk-in freezer/cooler. The condenser unit was installedin another chamber to control temperature. Instrumentation was added tothe system to measure refrigerant mass flow rate, refrigerant pressureand temperature before and after each component, air temperature andflow in/out of evaporator and condenser, and power to condensing unitand evaporator. Tests were run at one typical freezer temperatures (20°F.), and an ambient temperatures of 80° F. It should be noted that therefrigerant temperatures were typically 15° F. to 20° F. lower than thechamber temperatures. Table 1 shows performance results compared toR407C.

For these two blends, both capacity and COP do not change significantlyrespect of pure R407C. Therefore, addition of HMDS or HMDS/HCsolubilizing additives do not affect the system performance of anHFC-type fluid.

TABLE 1 Cooling Capacity Efficiency (COP) Refrigerant Tons % — % R407C2.13 100.0% 1.61 100.0% 96% R407C/4% HMDS 2.09 97.8% 1.65 102.5% 97%R407C/1% 2.09 98.1% 1.63 101.7% Isobutane/2% HMDS

Example 2 Compatibility of Materials

Solubiliizing additives such as HMDS could introduce undesirable effectsin certain components of the system. One of the most critical componentsis the expansion device because it is typically a flow restriction wheredeposition is possible. Standard industry tests are used to ensure nodeposition and/or flow restriction is caused by the additives introducedin the system. The most commonly used test is the “Capillary TubeClogging” test which consists of running a Standard refrigeration systemusing a capillary tube as a expansion device for a continuous period of2000 h. Capillary tubes are inspected and mass flow measured usingASHRAE Std 28-1988 (Method of Testing Capacity of Refrigerant CapillaryTubes) at 500 h, 750 h, 100 h and at the end of the test (2000 h).Variations of ±3% are considered normal because they inside the range ofexperimental uncertainty of the measurements. Table 2 shows resultsobtained for two tests:

1. R407C using POE oil as lubricant

2. A blend consisting of 90 wt. % R407C and 10 wt. % of HMDS usingMineral oil as lubricant.

Mass flow changes measured at the end of test 1 was of +1.29% asexpected for pure HFC with a compatible oil. Similarly, test 2 flowchange was +1.05%. Therefore both of them are within the range ofuncertainty proving the good compatibility of the HMDS with the mineraloil and other material present in the system.

TABLE 2 Refrigerant Mass Flow Change (%) 100% R407C +1.29% 90% R407C/10%HMDS +1.05%

Example 3 System Test with HFC/HMDS/HC Blends

This example demonstrates that an HFC/HMDS/HC blend has better oilreturn properties in the liquid receiver of a refrigeration system ascompared to a pure HFC. The intent of this experiment is to takeadvantage of the good solubility of high boiling hydrocarbons (e.g.Isobutane) but enhancing the solubility of the resulting blend by usingHMDS as a low boiling solubilizing additive. These tests used the sameequipment as described in Example 1, with the following modifications:

Two high-efficiency coalescent oil separators were added at thedischarge of the compressor, so the stream after them was oil-free(below 50 ppm). A continuous oil injection system was designed toextract oil from the compressor sump and inject it at the inlet of thecondenser, after the oil separators and before the liquid receiver (FIG.2). This system comprises a high pressure oil pump, a metering valve anda mass flow meter, so we could impose a desired Oil Circulation Ratio(OCR), which is a relation by mass between oil and the total mass flow(refrigerant plus oil). Two sight glasses were added to the horizontalliquid receiver, to visually observe any oil accumulating or dissolvingin the refrigerant. Oil circulation at the inlet of the liquid receiverwas measured directly using the system and oil flow meters shown in FIG.2. The OCR at the outlet of the receiver was measured using an oilseparator at the outlet of the evaporator, which sends the vapor back tothe system and the oil to flow meter. Verification measurements weredone by sampling before and after the liquid receiver to measuredirectly the amount of oil passing through. These tests consisted inimposing an OCR of 0.40% (oil by mass) at the inlet of the liquidreceiver and measuring it after. Table 3 shows results for the twoblends described in Example 1:

Blend 1: 96 wt. % of HFC (R407C) and 4 wt. % of HMDS

Blend 2: 97 wt. % of HFC (R407C), 2 wt. % of HMDS and 1 wt % ofisobutane

Both blends were successful in improving oil circulation, which is shownon Table 3.

TABLE 3 Oil Circulation Inlet Outlet Outlet Refrigerant (%) (%)Improvement (%) R407C 0.40% 0.10% — 96% R407C/4% HMDS 0.40% 0.35% +250%97% R407C/1% 0.40% 0.36% +260% Isobutane/2% HMDS

While the present invention has been particularly shown and describedwith reference to preferred embodiments, it will be readily appreciatedby those of ordinary skill in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe invention. It is intended that the claims be interpreted to coverthe disclosed embodiment, those alternatives which have been discussedabove and all equivalents thereto.

1. A composition comprising: (a) a refrigerant selected from the groupconsisting of a hydrofluorocarbon, hydrofluoroolefin, hydrofluoroether,and blends thereof; (b) a solubilizing agent comprising at least onesiloxane; and (c) a refrigeration system lubricant.
 2. The compositionof claim 1 wherein said siloxane is a compound of Formula (I):

wherein R₁-R₈ is independently H, C₁-C₄ alkyl, or C₆-C₁₀ aryl, and n isan integer from 0 to
 10. 3. The composition of claim 2 wherein n is 1 to4 and R₁-R₈ is independently H or C₁-C₃ alkyl, provided that a majorityR₁-R₈ is a C₁-C₃ alkyl.
 4. The composition of claim 3 wherein n is 0 or1 and R₁-R₈ is methyl or R₁-R₈ is ethyl.
 5. The composition of claim 4wherein said siloxane is hexamethyldisiloxane.
 6. The composition ofclaim 2 wherein said refrigerant is a C₁-C₆ hydrofluorocarbon.
 7. Thecomposition of claim 3 wherein said refrigerant is selected from thegroup consisting of: difluoromethane; 1,1,1,2,2-pentafluoroethane;1,1,1-trifluoroethane; 1,1,1,2-tetrafluoroethane; 1,1-difluoroethane; acombination of pentafluoroethane, tetrafluoroethane, andtrifluoroethane; a combination of pentafluoroethane and trifluoroethane;a combination of difluoromethane and pentafluoroethane; a combination ofdifluoromethane, pentafluoroethane, and tetrafluoroethane; and acombination of difluoromethane, pentafluoroethane, andtetrafluoroethane.
 8. The composition of claim 2 wherein saidrefrigerant is a C₂-C₆ hydrofluoroolefin.
 9. The composition of claim 8wherein said refrigerant is selected from the group consisting of: atrifluoropropene; a tetrafluoropropene; a pentafluoropropene; andmixture thereof.
 10. The composition of claim 9 wherein said refrigerantis selected from the group consisting of:(E)-2,3,3,3-tetrafluoropropene; (Z)-2,3,3,3-tetrafluoropropene;1,3,3,3-tetrafluoropropene, and (Z)-1,1,1,2,3-pentafluoropropene. 11.The composition of claim 2 wherein said refrigerant is a C₅-C₆hydrofluoroether.
 12. The composition of claim 1 wherein saidrefrigeration system lubricant is selected from the group consisting of:mineral oil, hydrocarbon oil, alkyl benzene oil, white or paraffinicoil, cycloparaffin, polyalkylene glycols, polyalkylene glycol esters,polyol esters, polyalphaolefins, and combinations thereof.
 13. Thecomposition of claim 1 wherein said solubilizing agent further comprisesat least one hydrocarbon selected from the group consisting of: C₁-C₆branched or straight chain alkane, alkene, or alkyl, and a C₃-C₆cycloalkane.
 14. The composition of claim 13 wherein said hydrocarbon isselected from the group consisting of methane, ethane, propane, propene,propyne, cyclopropane, 2,2-dimethylpropane, butane, isobutane,2-methylbutane, pentane, isopentane, 3-methylpentane, hexane,cyclohexane, isohexane, or combinations thereof.
 15. The composition ofclaim 14 wherein said refrigerant is present in amount of about 40 toabout 98.8 weight percent, said siloxane is present in an amount ofabout 0.1 to about 50 weight percent, said hydrocarbon is present in anamount of about 0.1 to about 10 weight percent, and said lubricant ispresent in an amount of about 1 to about 50 weight percent.
 16. Thecomposition of claim 14 wherein said refrigerant is present in amount ofabout 85 to about 98.8 weight percent, said siloxane is present in anamount of about 0.1 to about 10 weight percent, said hydrocarbon ispresent in an amount of about 0.1 to about 5 weight percent, and saidlubricant is present in an amount of about 1 to about 30 weight percent.17. A method for recharging a refrigerant system comprising: a. removingat least a portion of a chlorine-containing refrigerant from arefrigeration system comprising said chlorine-containing refrigerant anda lubricant, while retaining a majority of said lubricant in saidsystem; and b. adding a replacement refrigerant composition to saidrefrigeration system either subsequent to, or simultaneously with, saidremoving step, wherein said replacement refrigerant compositioncomprises a refrigerant selected from the group consisting ofhydrofluorocarbon, hydrofluoroolefin, hydrofluoroether, and blendsthereof; and a solubilizing agent comprising at least one siloxane and,optionally, at least one hydrocarbon selected from the group consistingof: C₁-C₆ branched or straight chain alkane, alkene, or alkyl, and aC₃-C₆ cyclic hydrocarbon.
 18. A method for improving the solubility of arefrigerant in a lubricant comprising: contacting a refrigerant selectedfrom the group consisting of a hydrofluorocarbon, hydrofluoroolefin,hydrofluoroether, and blends thereof, with a lubricant selected from thegroup consisting of mineral oil, hydrocarbon oil, alkyl benzene oil,white or paraffinic oil, polyalkylene glycols, polyalkylene glycolesters, polyol esters, polyalphaolefins, and combinations thereof,wherein said contacting is performed in the presence of a solubilizingagent comprising a siloxane, and optionally, at least one hydrocarbonselected from the group consisting of: C₁-C₆ branched or straight chainalkane, alkene, or alkyl, and a C₃-C₆ cyclic hydrocarbon.
 19. Arefrigerant composition comprising a refrigerant selected from the groupconsisting of a C₁-C₆ hydrofluorocarbon, C₂-C₄ hydrofluoroolefin, C₅-C₆hydrofluoroether, and blends thereof and solubilizing agent comprisingat least one siloxane selected from the group consisting ofhexamethyldisiloxane, octamethyltrisiloxane, and hexaethyldisiloxane,octaethyltrisiloxane.
 20. The refrigerant of claim 19 wherein saidsolubilizing agent further comprises at least one hydrocarbon selectedfrom the group consisting of C₁-C₆ branched or straight chain alkane,alkene, or alkyl, and a C₃-C₆ cyclic hydrocarbon.